1. Field of the Invention
The invention relates to a reticule or template for judging the print quality of a particular pattern used for finding an encoded pattern or symbol. More specifically, the invention relates to a reticule or template having a pattern of concentric rings or other geometrical shapes in an opposite-color arrangement with respect to a pattern used as an orientation target on a symbol, for determining if the symbol, such as a hexagonal code symbol, meets predetermined specifications.
2. Description of the Related Art
Various types of symbol codes are used on merchandise, such as boxes, letters, packages, etc., for encoding pertinent information about an article of merchandise. For example, universal product codes (also known as "bar codes") are typically placed on an outer surface of the merchandise in order to encode information related to the merchandise in a point-of-sale transaction. An example of such encoded information would be the type of merchandise.
Based on the scanned bar code, a memory is accessed at the point-of-sale location to determine the cost of the scanned article of merchandise. This determination is based on the decoded bar code information that identifies the type of merchandise being sold. For example, based upon a decoded sequence of numbers that correspond to the bar code on an article of merchandise, a lookup table storing the current price of the merchandise can be accessed.
Universal product codes (UPC) typically lack the data density in order needed for storing detailed information concerning the object on which the code is affixed. For example, lines of a UPC bar code vary in a range from about 1/8" to 1" in height, and from about 10 to 52 mils in thickness. For UPC bar codes, the spacings between the lines making up the bar code may be of various widths. The variations in the spacings are one element in determining the bar code characters making up the bar code. Bar code information is read by illuminating the bars and spacings in a sequential manner. The bars absorb light and the background spacings reflect light. The pattern of these reflections and nonreflections is sensed by a bar code scanner.
Conventional UPC bar codes require a large amount of space to encode detailed information concerning the article on which the bar code is carried. Therefore, other types of codes have been developed which encode a greater amount of information onto a smaller area. For example, U.S. Pat. No. 3,553,438 discloses wedged-shaped coded elements, U.S. Pat. No. 3,971,917 discloses concentric black and white bit-encoded rings, U.S. Pat. No. 4,286,146 discloses information encoded into contiguous squares and rectangles, and U.S. Pat. No. 4,488,679 discloses a densely packed data field of dots for encoding information.
The size and speed of modern conveyor systems, which carry packages of varying sizes with labels of encoded information affixed thereon, has created a need to utilize small, inexpensive and compact labels. U.S. Pat. No. 4,998,010 describes one such labeling approach, using a large number of contiguous hexagons within a 1".times.1" area. FIG. 1 shows a typical hexagonal coded symbol area 30, with a bull's eye center area 35 and a plurality of hexagons 20 placed at strategic locations outside of the bull's eye center area 35. The bull's eye is used as a locator as discussed further herein. The bull's eye is also used for alignment purposes before the encoded information that corresponds to the hexagons 20 can be electro-optically scanned. Once a hexagonal-code scanner is aligned with the bull's eye pattern 35, the information corresponding to the plurality of hexagons 20 can be read.
FIG. 1 also shows a maximum allowable area of the hexagonal coded symbol area 30, as given by lines 34H, 34V, and a minimum allowable area of the hexagonal coded symbol area 30, as given by lines 33H, 33V.
FIG. 2 shows a blow-up of an area of the contiguous hexagons 20 that are make up part of the encoded information in the hexagonal coded symbol area 30. As can be seen from FIG. 2, hexagonal shapes are well suited for encoding a large amount of information into a small area. The hexagons 20 fit within a "tiled array", with no wasted space between the hexagons 20. Referring back to FIG. 1, the total area that the hexagonal coded symbol area 30 encompasses is approximately 1".times.1" (0.981".times.0.981" square using the minimum allowable space within lines 34H, 34V of FIG. 1, 1.096".times.1.096" square using the maximum allowable space within lines 33H, 33V of FIG. 1). The bull's eye center circle 44 typically is not located at the midpoint of the hexagonal coded symbol area 30.
Within the approximately 1".times.1" code symbol region, there is room for about 888 hexagons. Each of those 888 hexagonal areas is set to have either a black interior color (i.e, inked hexagon) or a white interior color (i.e., non-inked hexagon). This type of encoding allows a large amount of data to be encoded within a very small area, and is well-suited for mail and package delivery services, which must accommodate packages and letters of all sizes. To be able to trace a package or letter through during the delivery process, there is a need to encode information concerning how the package is to be delivered, whether the package is fragile and/or needs special handling requirements, whether the package needs to be kept in a special environment during shipping (e.g., temperature or humidity restrictions), etc.
A hexagonal encoding system such as that described above was developed by United Parcel Service (UPS), and is used extensively by UPS and others in determining the status of packages as they are sent from an origination location, through a series of intermediate locations, and finally on to a destination location.
When affixing the hexagonal-encoded labels onto packages in a conveyor-type environment, care must be taken so that the labels are properly affixed to their respective packages. In addition, misalignment of the bull's eye center area may result in the hexagons of the hexagonal coded symbol area not being properly read by a hexagonal code scanning device or the hexagonal code scanning device not becoming aligned with the acquisition target (bull's eye). In either case, the scanner would not properly acquire the target and could not scan the hexagons making up the hexagonal coded symbol area.
In such a system, the bull's eye provides a finder pattern. Once the pattern is found, the code can be read. If the elements of the finder pattern vary too much in size (e.g., the print quality is not good), an imaging device might not find the bull's eye. If the bull's eye is not found, the scanner, which reads the symbol outward from the center of the hexagonal coded symbol area, cannot acquire the coded symbols and therefore cannot read them.
Boxes which become tilted produce an optically skewed image. If the bull's eye is within specifications, image processing techniques can be used to correct for the tilting. However, such correction is not possible if the bull's eye is not within specifications. Thus, there is a need to have a good tool for verifying a bull's eye within specifications.
U.S. Pat. Nos. 4,422,241, and 4,607,433, both invented by David Meeker, disclose a transparent plate mark locator for determining whether a postage indication on an envelope is within appropriate specified requirements. U.S. Pat. No. 4,149,070, invented by Louis Pastorius, discloses a device used to inspect a plurality of bars and spaces of a UPC bar code by comparing the sizes of the bars with a predetermined pattern of the bars.
In the Pastorius patent, the alignment of the bars on the template is used to determine if the bars of the actual bar code are correct. Pastorius does not disclose aligning the code with an "alignment" object before comparing the bars on the bar code with the predetermined bars on the template. In the Meeker patents, there is no direct overlay of a specified pattern on top of a similar pattern on the template. Meeker employs edge indications to line up with an envelope in order to determine if a postage label is within an allowable area as drawn on the template.
Accordingly, it is desirable to have a simple and inexpensive device that allows one to perform quality control of polygonal codes having acquisition targets, in order to determine, prior to scanning, if the print quality of the code symbol is adequate so that the code symbol can be found and read.